Area Forecast Discussion
Issued by NWS Northern Indiana

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717
FXUS63 KIWX 182007
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
307 PM EST Sat Nov 18 2017

.SYNOPSIS...
Issued at 249 PM EST Sat Nov 18 2017

Much colder air will sweep into the region this evening along with
strong and gusty north to northwest winds of 20 to 30 mph. Wind
gusts may reach 40 mph for a few hours this evening. Rain will
slowly diminish as well this evening but there will be a chance
for lake effect rain and snow showers closer to Lake Michigan
tonight into Sunday morning. Low temperatures will drop into the
lower 30s tonight and highs on Sunday will remain in the middle
30s.

The rest of the upcoming holiday week looks seasonably cool and
dry through Thanksgiving Day.

&&

.SHORT TERM...(This Evening through Sunday)
Issued at 249 PM EST Sat Nov 18 2017

A plethora of issues to contend with in the early part of this
short term period. Deepening surface low was moving through
northwest Ohio this afternoon and dragging a cold front through
behind it. Narrow line of convection moved through eastern areas
along warm front but remained below severe limits in our local
area as no reports were received. Thunder chances are quickly
diminishing and expect mainly rain remainder of afternoon into
evening.

Temperatures will continue to fall post frontal into this evening
with pcpn intensity dropping off quickly. Regional radar mosaic
shows plenty of wrap around pcpn upstream but hires model guidance
suggest drying aloft to quickly move east and will likely see much
of this erode during the early evening. Pcpn expected to end
before deeper cold air arrives and therefore do not expect much if
any snow on back side of this system outside of weak lake effect.

Winds will increase for a few hours into early evening as surface
low deepens and gradient tightens along with low level cold air
advection. Bufkit soundings and momentum transfer suggest a couple
hours of gusts to 35 knots away from the lake and around 40 knots
near lakeshore areas. This is shy of advisory criteria and will
handle with area wide special weather statement.

Deepening cold wedge overnight to increase delta T values over Lake
Michigan into upper teens and lower 20s. Model soundings show a
large dry wedge just above 5kft where strong inversion persists
through Sunday. Strong omega below this within saturated low levels
up to shallow inversion but DGZ remains well above dry layer and non-
saturated most of the night. Only toward 12-15z Sunday does DGZ
get to below the inversion with strongest cold air advection and
even then looks to be just above the saturated layer. Have stayed
with just low to mid chance pops for this event given the negative
factors.

High pressure will begin to nose into area on Sunday with clearing
away from the lake. Expect lake clouds to erode fairly quickly in
afternoon given return flow and exit of thermal trough along with
mid level dry air already in place. Temperatures will move little on
Sunday with highs remaining in the 30s.

&&

.LONG TERM...(Sunday Night through Saturday)
Issued at 249 PM EST Sat Nov 18 2017

A welcome quiet period in store for busiest travel days leading
up to Thanksgiving. Temperatures look to swing up and down with
several weak moisture starved synoptic systems passing through the
region.

First wave will pass on Tuesday. Main short wave energy and surface
low tracking well to our north but a decent cold front will sweep
southeast during the day. High pressure off the Atlantic and
stretching west to keep deeper moisture well south of the region.
Will keep forecast dry with this fropa. Rather strong baroclinic
zone and afternoon cold air advection which will likely lead to
falling temps if this timing holds.

High pressure back over the area on Wednesday with highs back in 30s
but with dry weather for travel. May be a few flurries or light lake
effect snow showers near Lake Michigan but at this time does not
look like much if any and no impacts. Another weak and moisture
starved cold front possible Thanksgiving Day which will keep
temperatures on the below normal side.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday Afternoon)
Issued at 1227 PM EST Sat Nov 18 2017

Sfc low pressure has reached central IN at the beginning of the
fcst period. the wmfnt extended newd through FWA into nw
Ohio.south of the low a line of tsra has developed from the late
morning hours and is advancing enewd. the sfc low will quickly
translate into Ohio this aftn and well east of the area by mid
evening. Will carry the precip until 23Z at KSBN then vicinity
while overnight. Will carry the precip at KFWA until mid evening
and then vicinity until 06Z. Winds are already nnw at KSBN and
will increase to above 20 kts with gusts to 30 kts by 23Z while
at KFWA winds will turn nw by 20Z and increase to above 20 kts
gusts to around 30 kts by 23Z. Expect IFR conds at KFWA this aftn
improving to LIFR later tonight while remaining predominately
LIFR at KSBN.


&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...Gale Warning until 4 AM EST Sunday for LMZ043-046.

&&

$$

SYNOPSIS...Lashley
SHORT TERM...Lashley
LONG TERM...Lashley
AVIATION...Frazier


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